1. Field of the Invention
The present invention relates to a laser processing method for forming a laser processed groove on a nonlinear crystal substrate of lithium tantalate (LiTaO3) or lithium niobate (LiNbO3), for example.
2. Description of the Related Art
In a semiconductor device fabrication process, a plurality of crossing division lines are formed on the front side of a substantially disk-shaped silicon substrate to thereby partition a plurality of regions where devices such as ICs and LSIs are respectively formed, thus forming a semiconductor wafer having the devices partitioned by the division lines on the front side. The semiconductor wafer is cut along the division lines to thereby divide the regions where the devices are formed from each other, thus obtaining the individual devices. Further, an optical device wafer is provided by forming gallium nitride compound semiconductors or the like on the front side of a sapphire substrate or a silicon carbide substrate. The optical device wafer is also cut along the division lines to obtain individual optical devices divided from each other, such as light emitting diodes and laser diodes, which are widely used in electric equipment.
As a method of dividing such a wafer along the division lines, there has been proposed a method including the steps of applying a pulsed laser beam having an absorption wavelength to the wafer along the division lines to thereby form laser processed grooves as a break start point on the wafer along the division lines and next applying an external force to the wafer along the division lines where the laser processed grooves as the break start point are formed, thereby breaking the wafer along the laser processed grooves (see Japanese Patent No. 3408805, for example).